Diagram caption: The constellation Octans along with its bright stars and its surrounding constellations. Octans is surrounded by (going clockwise from the top): Hydrus, Indus, Pavo, Apus, Chameleon and Mensa. Octans is a relatively faint constellation that is notable as it lies at the south celestial pole. While the northern pole star is the relatively bright Polaris, sigma Octans, the southern pole star, is barely visible with the naked eye.

Octans lies at the south celestial pole and is thus visible from the whole southern hemisphere with some of the constellation visible from equatorial regions of the northern hemisphere. The constellation is circumpolar for most of the southern hemisphere. It is best viewed in the evening in the northern hemisphere autumn and southern hemisphere spring.

This diagram maps an area around the south celestial pole. Here lines of constant right ascension converge. The right ascension values of these lines (in hours) are marked on the x-axis above and below the diagram. The solid circle around the pole marks a line of -80° declination with the larger, incomplete circle to the right marking -70° declination. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.

Diagram credit: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope. Credit Link

Related glossary terms: Apparent Magnitude , Celestial Coordinates , Constellation , Declination , Polaris , Right Ascension (RA) , South Celestial Pole (SCP)
Categories: Naked Eye Astronomy

Diagram license: Creative Commons Attribution 4.0 International (CC BY 4.0) Creative Commons Attribution 4.0 International (CC BY 4.0) icons